RCLED - Crosslight Software

Analysis of Resonant-Cavity
Light-Emitting Diodes
Copyright 2006 Crosslight Software Inc.
www.crosslight.com
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Contents
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About
About RCLED.
RCLED.
Crosslight’
ss model.
Crosslight’
model.
Example
Example of
of an
an InGaAs/AlGaAs
InGaAs/AlGaAs RCLED
RCLED
with
with experimental
experimental verification.
verification.
Example
Example of
of aa VCSEL-like
VCSEL-like RCLED
RCLED of
of
GaAs/AlGaAs
GaAs/AlGaAs MQW.
MQW.
RCLED
RCLED with
with detuned
detuned DBR.
DBR.
RCLED
RCLED with
with long
long cavity.
cavity.
Conclusions.
Conclusions.
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About RCLED
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RCLED
RCLED takes
takes advantage
advantage of
of
microcavity
microcavity effects
effects to
to enhance
enhance
spontaneous
spontaneous emission.
emission.
Narrower
Narrower spectrum
spectrum linewidth.
linewidth.
Superior
Superior directionality
directionality of
of emission
emission
with
with better
better LED-fiber
LED-fiber coupling.
coupling.
Potential
Potential as
as light
light source
source for
for recent
recent
plastic
plastic optical
optical fiber
fiber (POF)-based
(POF)-based local
local
area
area networks.
networks.
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Crosslight RCLED model
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Self-consistent
Self-consistent calculation
calculation of
of material
material spontaneous
spontaneous
emission
emission rate
rate based
based on
on rigorous
rigorous quantum
quantum well/dot
well/dot
spectrum
spectrum theories
theories coupled
coupled with
with 2/3D
2/3D simulation
simulation of
of current
current
injection
injection from
from the
the Crosslight
Crosslight APSYS
APSYS drift-diffusion
drift-diffusion solver.
solver.
Coupling
Coupling of
of spontaneous
spontaneous emission
emission with
with microcavity
microcavity modes
modes
based
based on
on theory
theory of
of C.
C. H.
H. Henry
Henry (1986)
(1986) [1].
[1].
Henry’
ss theory
Henry’
theory has
has been
been extended
extended from
from waveguide
waveguide to
to
RCLED
RCLED by
by proper
proper accounting
accounting of
of mode
mode densities
densities in
in aa quasiquasi2D/3D
2D/3D emission
emission situation.
situation.
Photon
Photon recycling
recycling effects
effects taken
taken into
into account
account by
by accurate
accurate
determination
determination of
of photon
photon power
power density
density inside
inside the
the RCLED
RCLED
and
and self-consistent
self-consistent model
model of
of material
material gain/loss
gain/loss of
of the
the
quantum
quantum wells/dots.
wells/dots.
[1] C. H. Henry, "Theory of spontaneous emission noise
in open resonators and its application to lasers and optical amplifiers,"
J. Lightwave Technol., vol. LT-4, pp. 288--297, March 1986.
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Contents
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About
About RCLED.
RCLED.
Crosslight’
ss model.
Crosslight’
model.
Example
Example of
of an
an InGaAs/AlGaAs
InGaAs/AlGaAs RCLED
RCLED
with
with experimental
experimental verification.
verification.
Example
Example of
of aa VCSEL-like
VCSEL-like RCLED
RCLED of
of
GaAs/AlGaAs
GaAs/AlGaAs MQW.
MQW.
RCLED
RCLED with
with detuned
detuned DBR.
DBR.
RCLED
RCLED with
with long
long cavity.
cavity.
Conclusions.
Conclusions.
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Structure
Structure
Based on Schubert et. al,
J. Lightwave Technol., vol.
14, p. 1721
Simulation
Simulation Mesh
Mesh
MQW and
Optical
Region
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2/3D
-Diffusion Model
2/3D Drift
Drift-Diffusion
Model
3D Potential
distribution
MQW Region
Distribution of ycomponent of
electronic current
DBR Region
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True
True Physical
Physical Simulation
Simulation in
in 3D
3D
Conduction band
Electron IMREF
Hole IMREF
Valence band/LH/HH
True 3D simulation of band structure physics including MQW
strain effects. Current flow and self-heating may be included
self-consistently in 3D.
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Standing
Standing Wave
Wave and
and Carrier
Carrier Generation
Generation
Power density relative to
spontaneous emission
power in z-direction
Carrier generation rate due to
high optical power within the
LED cavity. Absorption at
MQW calculated selfconsistently using interband
transition models.
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Standing
Standing Wave
Wave and
and Index
Index
MQW
Refractive
index
Re-scaled power density
Remark: The reflection phase of the Ag. Mirror is adjusted so
that antinode of standing wave aligns with the MQW region.
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Photon
Photon Recycling
Recycling and
and IQE
IQE
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Self-pumping
Spont.
Em.
ReAbsorp.
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High
High mirror
mirror reflectivity
reflectivity è
è higher
higher
photon
photon density
density in
in cavity
cavity under
under
resonant
resonant condition.
condition.
Re-absorbed
Re-absorbed photons
photons è
è higher
higher
photo
photo carrier
carrier densities
densities (self(selfphoto-pumping).
photo-pumping).
Higher
Higher carrier
carrier concentration
concentration è
è
more
more photon
photon emission
emission by
by
spontaneous
spontaneous emission
emission (enhanced
(enhanced
by
by microcavity
microcavity resonance).
resonance).
Actual
Actual spontaneous
spontaneous emission
emission rate
rate
substantially
substantially higher
higher than
than current
current
injection
rate.
injection rate.
IQE
IQE calculation
calculation =
= spontaneous
spontaneous
emission
rate
subtracting
emission rate subtracting photon
photon
absorption
absorption rate,
rate, dividing
dividing current
current
injection
injection rate.
rate.
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Improvement
Improvement in
in Spectrum
Spectrum Linewidth
Linewidth
MQW
material
emission
without RC
effects
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from 2.5
to 10 mA
injection
Simulated EL
emission
from bottom
facet of
RCLED.
Experimental
Data taken from
Schubert et. al,
J. Lightwave
Technol., vol. 14,
p. 1721
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Angle
Angle Dependence
Dependence in
in EL
EL Spectrum
Spectrum
Remark: For well tuned DBR
/cavity-length and high Q
cavity, only a single
emission peak at normal
direction is significant.
More details
near low
intensity region
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Contents
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About
About RCLED.
RCLED.
Crosslight’
ss model.
Crosslight’
model.
Example
Example of
of an
an InGaAs/AlGaAs
InGaAs/AlGaAs RCLED
RCLED
with
with experimental
experimental verification.
verification.
Example
Example of
of aa VCSEL-like
VCSEL-like RCLED
RCLED of
of
GaAs/AlGaAs
GaAs/AlGaAs MQW.
MQW.
RCLED
RCLED with
with detuned
detuned DBR.
DBR.
RCLED
RCLED with
with long
long cavity.
cavity.
Conclusions.
Conclusions.
Structure
Structure of
of AlGaAs
AlGaAs RCLED
RCLED
Top DBR
Implanted
current
confinement
region
MQW
Bottom DBR
A VCSEL-like structure with fewer layer pairs in top DBR to help power
extraction. Ion implantation is used to form current confinement.
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2/3
-Diffusion Model
2/3 Dim
Dim Drift
Drift-Diffusion
Model
Y-component of electron current distribution in RCLED. Please
note the strong (blue) current crowding area which causes optical
gain to help amplify the optical waves there.
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RCLED
RCLED Performance
Performance
(b)
(a)
(a)
Internal efficiency of near unity.
(b)
Extraction efficiency from top
facet.
(c)
Total EL power versus injection
current.
(c)
Current
Current Crowding
Crowding Effects
Effects
MQW spontaneous emission
distribution under top aperture.
Lateral distribution is due to
current crowding.
Standing wave shows strong lateral
variation due to gain/’spontaneous
emission rate distribution.
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Standing
Standing Wave
Wave Alignment
Alignment
Index profile
MQW
Scaled
power
Remark: Effective cavity length near the MQW should be (n+1/2)
wavelength to ensure antinode of standing wave aligns with MQW.
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Angular
Angular dependence
dependence of
of EL
EL spectrum
spectrum
Detailed view of lower
power regime of the above
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Contents
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About
About RCLED.
RCLED.
Crosslight’
ss model.
Crosslight’
model.
Example
Example of
of an
an InGaAs/AlGaAs
InGaAs/AlGaAs RCLED
RCLED
with
with experimental
experimental verification.
verification.
Example
Example of
of aa VCSEL-like
VCSEL-like RCLED
RCLED of
of
GaAs/AlGaAs
GaAs/AlGaAs MQW.
MQW.
RCLED
RCLED with
with detuned
detuned DBR.
DBR.
RCLED
RCLED with
with long
long cavity.
cavity.
Conclusions.
Conclusions.
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Detuning
Detuning DBR/Cavity
DBR/Cavity
Alignment of
wave at
oblique
maximum
power
direction with
refractive
index profile.
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There
There may
may be
be applications
applications of
of RCLED
RCLED to
to control
control
the
the direction
direction of
of major
major resonant
resonant peak
peak at
at an
an
oblique
oblique angle.
angle.
Take
Take similar
similar VCSEL-like
VCSEL-like structure
structure with
with longer
longer
cavity
cavity and
and slightly
slightly reduced
reduced DBR
DBR periods.
periods.
Detuning
Detuning at
at normal
normal direction.
direction.
Engineering
Engineering the
the Emission
Emission Angle
Angle
Remark: Major emission at an oblique angle means ring-like
emission pattern in real space.
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Contents
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About
About RCLED.
RCLED.
Crosslight’
ss model.
Crosslight’
model.
Example
Example of
of an
an InGaAs/AlGaAs
InGaAs/AlGaAs RCLED
RCLED
with
with experimental
experimental verification.
verification.
Example
Example of
of aa VCSEL-like
VCSEL-like RCLED
RCLED of
of
GaAs/AlGaAs
GaAs/AlGaAs MQW.
MQW.
RCLED
RCLED with
with detuned
detuned DBR.
DBR.
RCLED
RCLED with
with long
long cavity.
cavity.
Conclusions.
Conclusions.
InGaN
InGaN LED
LED Structure
Structure
Structure taken from: Horng et. al. IEEE Photonic Tech. Lett.,
Vol. 18, p. 457, 2006
Simulated electron
current flow pattern.
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Standing
Standing Wave
Wave at
at Normal
Normal Direction
Direction
MQW
Index profile
Power density
DBR
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Multiple
Multiple Resonance
Resonance Peaks
Peaks as
as Compared
Compared with
with Experiment
Experiment
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Conclusions
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A
A comprehensive
comprehensive physical
physical model
model of
of resonant
resonant
cavity
cavity has
has been
been incorporated
incorporated into
into
Crosslight’
ss APSYS/LED
Crosslight’
APSYS/LED modules.
modules.
Based
Based on
on rigorous
rigorous theory
theory describing
describing
interaction
interaction of
of spontaneous
spontaneous emission
emission
spectrum
spectrum with
with microcavity
microcavity modes.
modes.
Resonant
Resonant effects
effects in
in spatial,
spatial, spectral
spectral and
and
angular
angular dimensions
dimensions have
have been
been obtained
obtained in
in
reasonable
reasonable agreement
agreement with
with experiments.
experiments.
Self-consistent
Self-consistent integration
integration with
with the
the main
main
APSYS
APSYS simulator
simulator enables
enables all-in-one
all-in-one analysis
analysis
and
and design
design approach.
approach.